type MyNumber = number;
export function sum(n1: number, n2: number) {
  return n1 + n2;
}
export function sub(n1: number, n2: MyNumber) {
  return n1 - n2;
}
export function formatPrice(price: string | number): Promise<string> {
  return new Promise((resolve, reject) => {
    if (typeof price === 'string' && price.includes('$')) {
      resolve(price);
    } else {
      resolve(price + '$');
    }
  });
}
